Role of Fine Needle Aspiration Cytology in Diagnosis of Solitary Thyroid Nodules

Introduction: This study was conducted at the Department of ear, nose, throat, head and neck surgery, Post Graduate Medical Institute Lady Reading Hospital Peshawar. The duration of the study was one year from June 17, 2009 to June 16, 2010. The sample size was 82 patients with solitary thyroid nodule, fulfilling the inclusion criteria. After taking detailed history, thorough examination, relevant investigation and informed consent fine needle aspiration cytology was performed in all cases by the same cytopathologist. Thyroid surgery was performed and specimens were examined by the same histopathologist. The statistical analysis was performed using the statistical program for social sciences (SPSS version 11). Materials and Methods: Our study included 82 cases consisting on 57 female and 25 male, with female: male ratio of 2.28: 1.The age of the patients was ranged from 16-65 years with mean age of 42.56 + S.D 11.60 years. Most of the patients presented in 3rd and 4th decade followed by the 5th and 2nd decade. The diagnostic yield of Fine Needle Aspiration Cytology (FNAC) in this study was accuracy 82.92%, sensitivity 88.09%, specificity 77.50% and positive predictive value was 80.43%. Results: One hundred twenty six patients entered the study among which 77 (61%) were female and 49 (39%) male. Mean age was obtained as 26.9 ± 7.7 yrs. Up to 79.4% of patients had complaints concerning the cosmetic outcomes, 39.7% with respiratory and 4.8% with olfactory problems. The reason to sue the physician had a significant relationship with the patients’ age and sex, and also with the surgeons’ experience. Conclusion: FNAC has key rule in diagnosis of solitary thyroid nodule because it is safe, minimally invasive and cost effective diagnostic tool.


Introduction
Frequency of thyroid disease is common in Pakistan and solitary thyroid nodule presents a significant diagnostic dilemma for the treating surgeon (1). Thyroid nodule occurs in 4-7% of the population (2). Malignant tumors of thyroid gland represent less than 0.5% of all cancers (3). Although solitary thyroid nodules are common in females, they are more likely to be malignant in males (4). Different imaging techniques are now used for pre operative diagnosis of solitary thyroid nodule like radio nucleotide scanning, high resolution ultrasonography etc. but fine needle aspiration cytology is regarded as the single and most cost-effective procedure (5). Fine needle aspiration cytology of malignant thyroid nodules reported to have sensitivity and specificity ranges from 65-98% and 72-100% respectively (6). Although there is a large body of world literature claiming the accuracy and usefulness of thyroid cytology, there is also evidence of showing possible limitations and pitfalls of this procedure (7). Fine needle aspiration cytology of thyroid gland is now a well established, first line diagnostic test for the evaluation of diffuse thyroid lesion as well as of solitary thyroid nodule with main purpose of confirming benign lesion and by reducing unnecessary surgery (8).
Virtually any disease of thyroid can be presented as a nodule and it is not usually possible to distinguish between benign and malignant thyroid nodule by any non invasive procedure (9). Use of FNAC for Thyroid enjoys unmatched popularity as it is predominantly related to the cosmetic complication and technical difficulties of thyroid surgery and relatively small number of true neoplasms in patients with thyroid nodules (10 Thyroid surgery was performed and specimens were examined by the same histopathologist. The statistical analysis was performed using the statistical program for social sciences (SPSS version 11). The frequencies and percentages were presented for qualitative variables and Mean + SD were presented for quantitative variables. All the relevant information was documented on a pre-designed proforma.
Sensitivity, specificity, positive predictive value and negative predictive value were calculated for fine needle aspiration cytology taking histopathologic examination as gold standard.

Results
Our     The diagnostic value of FNAC in this study was as follows: 37 cases (45.12%) were true positive, while 31 cases (37.80%) were true negative. In this study false positive cases were 9 (10.97%), 5 cases were follicular neoplasm on FNAC while on histopathology they turned out to be benign thyroid diseases, 3 cases were papiillary carcinoma which had been diagnosed benign thyroid cyst on biopsy (Table 4).
In our study 5 cases (6.09%) were false negative, 3 cases were benign thyroid diseases which were diagnosed papillary carcinoma on histopathology, 2 cases (2.43%) were diagnosed aslymphoma and follicular adenoma on histopathology (Table 5).    (11). Nonetheless, it is widely accepted that presently, FNAC is the best and most reliable diagnostic tool for use in the preoperative management of patients with such lesions. Thyroid nodule is more common in females than males. In this study there were 57 females and 25 males, with female: male ratio of 2.28: 1, which is comparable to the studies conducted nationally and internationally (12). In this study most of the patients presented in 3 rd and 4 th decade which is in accordance to the study of Bukhari and collegues (13). In this study the FNAC finding was as follows: 58 cases (70.73%) had non neoplastic lesions which in accordance to study of Korah (14) reporting benign lesions 69%, while in some of the studies benign lesions were found in 50% cases (15). Nodular goitre was the most common finding among the benign lesions (51.21%) which agrees with studies of Gupta (16) revealed 39 cases (52%) as colloid nodular goitre and Saddique (17).

Conclusion
FNAC has key rule in diagnosis of solitary thyroid nodule because it is safe, minimally invasive and cost effective diagnostic tool for preoperative assessment of patients with thyroid nodule to help the surgeon in management of these nodules.